How exactly does http://translate.wordpress.org work?

I notice that people have contributed a lot, and yet, the translation are not available.

e.g. At http://translate.wordpress.org/projects/bbpress/plugin there are plenty of items listed as “Waiting”. e.g. Polish, Romanian, French and Czech have 0% translation completed, but almost 100% strings in “waiting”.

Similarly, at http://translate.wordpress.org/projects/buddypress/dev Danish, Romanian, and Czech have almost 0% translation completed, but almost 100% strings in “waiting”.

This has been the status for many months (I am not exaggerating in the least). So how do we move strings from “waiting” to “translated”?